Abstract:

This article investigates influence of the steam explosion pretreatment method at different temperatures on sugar conversion rates and bioethanol production efficiencies from floodplain meadow hay. Floodplain meadow hay is used as a raw material, because these semi-natural grasslands need regular maintenance to preserve their high biodiversity. So far, this biomass has been largely unused, but it could provide a good feedstock for bioethanol production. In this work, steam explosion pretreatment is used in combination with enzymatic hydrolysis. Effects of steam explosion pretreatment on the fibre content and cell wall structure are also studied. Results from fibre analysis show, that the floodplain meadow hay has very high lignin content of 24.16%, but relatively low cellulose content of 27.19%. Highest cellulose to glucose conversion rate of 234.6 g kg-1 and ethanol yield of 115.7 g kg-1 of biomass were achieved with the steam explosion pretreatment at 200°C. Scanning electron microscope (SEM) images show that pretreatment at 150°C does very little damage to plant cells, while steam explosion at 200°C disintegrates most of the plant cell walls and exposes cellulose fibres.

Influence of harvesting time on biochemical composition and glucose yield from hemp

Abstract:

Abstract. This article investigates the influence of different harvesting times of hemp samples on their biochemical composition and glucose conversion yield. Samples were harvested from experimental fields of the Estonian University of Life Sciences from July to September in 2011. Dilute sulfuric acid solution was used for pretreatment in combination with enzymatic hydrolysis. Results indicate that the highest glucose conversion rate of 204.1 g kg-1 of dry matter of biomass was achieved by samples harvested on the 18th of August. The lowest glucose yield of 170.3 g kg-1 was achieved by samples harvested on 25th of August, which also had a very low hydrolysis efficiency of 46.9%. Biochemical composition and glucose conversion efficiencies of samples vary in time. Samples harvested in September have higher cellulose and lignin content than samples harvested in July. However, glucose conversion efficiencies decrease significantly in later samples. Average hydrolysis efficiency was 51.4%.

Influence of different pretreatment methods on bioethanol production from wheat straw

Abstract:

Article investigates the influence of different pretreatment methods on sugar
conversion and bioethanol production. Different dilute acid and alkaline pretreatment methods
are compared to determine the best pretreatment method to give the highest glucose and ethanol
yields under the mild operating conditions. Wheat straw is used as a raw material as it is the
most widely grown cereal in Europe. Dilute sulfuric acid, hydrochloric acid, nitric acid and
potassium hydroxide solutions are used for pretreatment in combination with enzymatic
hydrolysis. Results indicate that the highest cellulose-to-glucose conversion rate of 316.7 g kg-1
of biomass is achieved by the pretreatment with nitric acid. The lowest glucose concentration of
221.3 g kg-1 is achieved by hydrochloric acid. In the wheat straw samples pretreated with
sulfuric acid and KOH, two different approaches are used. Solid phase of half the samples is
rinsed with water before adding enzymes, and the rest of the samples are not. The rinsed
samples pretreated with KOH solution give the highest ethanol yield of 104.3 g kg-1, while the
lowest ethanol yield is 67.7 g kg-1 from samples pretreated with HCl solution. Unrinsed samples
and rinsed samples pretreated with sulfuric acid give an ethanol yield of 78.7 g kg-1 and
92.0 g kg-1, respectively. These results indicate that rinsing the solid phase of the samples with
distilled water before hydrolysis removes most of the inhibitory compounds formed during the
pretreatment with dilute acid and increases fermentation efficiency by approximately 12%.